Pseudo Philo Biblical Antiquities 32:4
4 And when his father had placed him upon the altar and had bound his feet to kill him, the Almighty quickly sent forth his voice from above saying: "Do not kill your son, nor destroy the offspring of your body: for now I have made myself known to those who are unaware of me, and have silenced those who constantly speak ill of you. And your memory shall be before me forever, and your name and the name of this your son from one generation to another."
Augustine City of God 11.32
On the City of God Against the PagansAmong other things, of which it would take too long time to mention the whole, Abraham was tempted about the offering up of his well-beloved son Isaac, to prove his pious obedience, and so make it known to the world, not to God. Now every temptation is not blame-worthy; it may even be praise-worthy, because it furnishes probation. And, for the most part, the human mind cannot attain to self-knowledge otherwise than by making trial of its powers through temptation, by some kind of experimental and not merely verbal self-interrogation;
Notes and References
"... in interpreting in this way, these writers seemed to contradict what the Bible itself says explicitly later on. For in the biblical account, after Abraham has demonstrated his willingness to offer up his beloved Isaac, God says to him: 'Now I know that you fear God, since you have not withheld your son, your only son, from me' (Genesis 22:12). 'Now I know' seems to imply 'I did not know before.' How then could the author of Jubilees and other interpreters maintain that God did know all along? The answer lies in yet another ambiguity in the Hebrew. For the same consonants that spell the Hebrew word 'I know' can also be read in such a way as to mean 'I have made known' or 'I have notified.' This is apparently how some interpreters chose to understand the text ... Thus, God's great test of Abraham took place in response to a challenge and was carried out in order to prove Abraham's virtues not to God, but to others—Satan, the other angels, or the world at large ..."
Kugel, James L. The Bible as it Was (pp. 172-173) Harvard University Press, 1998